1. The Field of the Invention
Implementations of the present invention relate to a propeller blades and systems and components employing propeller blades.
2. Discussion of the Relevant Art
Propellers are bladed rotating devices that move fluids. Typically, as the propeller rotates the device moves through the fluid. A pump is a propeller within a conduit, which moves fluid past itself. Conventional propellers and propeller blades are typically designed using a combination of the principles behind the Archimedes screw and the fluid dynamic principles of Bernoulli. Specifically, propellers typically replace the helical shape of an Archimedes screw with multiple blades to improve the entrance of the fluid into the shape of the device. Additionally, each of the blades in turn typically has a twisted airfoil shape.
The motion of the fluid over a conventional airfoil-shaped blade causes a low or even negative pressure on the top of the airfoil, or in other words, the front surface of the propeller blade. The combination of the positive force acting on the back surface of the blade and the low or negative pressure on the front surface of the blade causes the blade to move fluid. When the speed of a blade through a fluid is great enough, the fluid can vaporize into a gas (i.e., cavitation). The low pressure region created by the airfoil shape of conventional blades can be especially prone to cavitation. If the pressure of the liquid at any point along the low pressure surface drops below the vapor pressure of the liquid, the liquid will transform into gaseous bubbles. The presence of cavitation along any surface of a blade can be very harmful to the overall performance of the propeller. For example, cavitation can cause the propeller to stall, generate noise, cause erosion and other damage of components, cause vibration, and create a loss of efficiency.
In addition to cavitation, conventional propeller blades can cause fluid to flow radially outward and over the top edge of the blade. The fluid flow over the top edge of conventional blades can create eddies. These fluid eddies reduce the efficiency of the propeller and can give rise to significant noise. Furthermore, in the case of a pump, the radial force that conventional blades impart to the fluid can project the fluid into the walls of the conduit, thereby causing noise and a loss of efficiency.
Accordingly, there are a number of disadvantages in conventional propeller blades that can be addressed.